Mechanical seal assembly

ABSTRACT

A mechanical seal assembly having multiple compression spring assemblies that are used to bias a stationary seal into sealing engagement with a rotating seal, the springs in the spring assemblies being supported on their internal diameter and having their outside diameter visible for their entire length, each spring assembly further including a releasable, expendable clip that serves to preload the two seal faces against one another, limits relative axial movement between the stationary and rotating seal assemblies, and coaxially aligns the stationary and rotating seal assemblies.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to mechanical seals and, moreparticularly, to a mechanical seal assembly of a cartridge type havingmeans for maintaining alignment and preloading between the stationaryand rotating portions of the seal assembly.

2. Description of the Background

Numerous different mechanical seals have been proposed to effect sealingaround a shaft to prevent leakage of both sealing fluid and operatingfluid from an enclosure from which the shaft extends. While mechanicalseals employing a single biasing spring coil are known, typically, wherehigh speeds are involved, multiple, small coil springs are used, thecoil springs being circumferentially spaced around the rotary unit. Bothcompression springs and tension springs have been used as means to biasthe rotating and stationary seal faces together.

To the extent known by the Applicant, in a case where the springs areused to bias the stationary seal member, and particularly where thesprings are mounted externally of the process fluid, the springs aresupported on their outside diameter, usually contained in pockets in aseparate spring housing or the like that attaches to the main housing orgland of the seal, or in the main housing itself.

Mechanical seal designs employing compression springs that are supportedon their outside diameter, e.g., in spring pockets in the main or aseparate spring housing, frequently encounter problems because ofclogging sources such as coking, oxidation, salts from fluids thatcrystallize, contaminants from slurries, etc. This clogging restrictsthe springs' ability to provide axial closing force to the seal face.Additionally, mechanical seals wherein the springs are locatedinternally, i.e., in an area where they are contacted by any corrosivefluid (process fluid) that leaks past the seal, are subject to stresscorrosion cracking.

In addition to avoiding the clogging and corrosion problems discussedabove with respect to many prior art mechanical seal designs, it is alsodesirable that the biasing springs be subject to complete visualinspection while in service. If the springs are located in springpockets or separate spring housings or disposed directly behind the sealelement being biased, this becomes virtually impossible.

Accordingly, there remains a need for a mechanical seal design employingcompression springs, especially compression springs that act to bias thestationary seal element against the rotating seal element, that aresupported on their inside diameters, that are not subject to clogging,that are located externally of the process fluid environment so as to beremoved from corrosive environments, and that are subject to completevisual inspection.

It is common in integrated or cartridge-type mechanical seal designs,for ease of installation, to employ some sort of setting clips thatbasically hold the rotary and stationary components together while theseal is installed to minimize installation time and misalignment ofcomponents. Many existing designs utilize setting clips that are rigidlysecured to the various seal parts using screws or other fasteners.Obviously, these clip types with their fasteners must be repositioned orremoved prior to operation of the seal. There are yet other designs thatutilize removable, flexible setting straps or a setting means made of awearable material, the latter not requiring removal.

It would clearly be desirable to have a cartridge-type assembly thatutilizes wearable setting clips and therefore is easily installed, thatholds the components of the seal assembly together in both axialdirections along the shaft and concentrically positions the rotary partsrelative to the stationary parts prior to and during installation, andthat need not be repositioned or removed prior to operation of themechanical seal.

Mechanical seals of the type under consideration include a glandassembly that is used to secure and seal the mechanical seal assembly tothe housing through which the shaft extends. For example, in a typicaluse of a mechanical seal to effect sealing of a pump shaft, the gland ispositioned around the pump shaft and secured by bolts to the pumphousing. Typically, this is accomplished by means of threaded bolts thatare received in threaded bores in the pump housing and extend throughsuitable apertures in the gland body or in tabs or lugs carried by thegland body of the mechanical seal. When the tabs or lugs are monolithicwith the gland or must be installed as part of the gland, difficulty isoften encountered because of tight spacing. Accordingly, it wouldclearly be desirable to have a gland assembly for use with a mechanicalseal, which would allow the gland assembly to be positioned on the shaftand have removable tabs or lugs, which, once the gland is positioned onthe shaft, can be easily affixed to the gland, following which the tabsor lugs can be used to secure the gland to the housing as describedabove.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved mechanical seal assembly.

Yet another object of the present invention is to provide an improvedmechanical seal assembly of the cartridge type that employs externallymounted biasing springs.

A further object of the present invention is to provide a mechanicalseal assembly that uses biasing springs that are resistant to clogging.

A further object of the present invention is to provide a mechanicalseal assembly using compression springs that are supported on theirinside diameter so as to permit complete visual inspection of thespring.

Still a further object of the present invention is to provide acartridge-type mechanical seal assembly that utilizes wearable,temporary setting clips that act to hold the components of the sealassembly together in both axial directions along the shaft andconcentrically position the rotary parts relative to the stationaryparts of the seal.

It is yet another object of the present invention to provide a glandassembly for use with a mechanical seal that uses removable tabs or lugsto secure the gland of the mechanical seal to the housing of the machineshaft being sealed.

The above and other objects of the present invention will becomeapparent from the drawings, the description given herein, and theappended claims.

In one aspect, the mechanical seal of the present invention, which isused to effect sealing between a rotatable shaft and a wall throughwhich the shaft extends and rotates relative thereto, comprises anannular sleeve for securing to the shaft. A first annular seal elementis carried by the sleeve and rotates therewith in response to rotationof the shaft, the first seal element having a first seal face. Anannular housing or gland is provided for securing to the wall, and asecond, annular seal element is interconnected to the housing and has asecond seal face engageable with the first seal face. The seal assemblyfurther includes a plurality of compression spring assemblies forbiasing the second, stationary seal towards the first seal. Each of thecompression spring assemblies includes a pin member attached to thehousing, the pin member being disposed generally parallel to the sleeve,there being provided a stop member carried by the pin member and locateddistal the housing. The compression spring assembly further includes acompression ring having a first side operatively engageable with thesecond seal element and an opposite, second side. The spring assembliesalso include a compression spring disposed in surrounding relationshipto the pin member, i.e., supported on the inside diameter, andcompressed between the second side of the compression spring and thestop member such that the compression spring serves to bias the secondseal element against the first seal element. The compression ring isunsupported on its outside diameter for its entire length and thereby isreadily susceptible to visual inspection.

In yet another embodiment of the present invention, the mechanical sealcomprises a rotating seal assembly including an annular sleeve forsecuring to the shaft and a first annular seal element carried by thesleeve and rotatable therewith in response to rotation of the shaft, thefirst seal element having a first seal face. The mechanical seal furtherincludes a stationary seal assembly comprising an annular housing orgland for securing to the wall of the machine housing through which ashaft extends, a second annular seal element interconnected to thehousing and having a second seal face engageable with the first sealface, biasing means for urging at least one of the first or second sealelements towards the other of the first or second seal elements wherebythe first and second seal faces are sealingly engaged. There is alsoprovided selectively releasable means interconnecting the rotating sealassembly and the stationary seal assembly to restrain relative axialmovement between the rotating and stationary seal assemblies prior tosecuring the housing to said wall and to effect a preload of the biasingmeans.

In another aspect of the present invention, there is provided a glandassembly for use in mounting a mechanical seal about a machine shaft tothe wall of a machine housing through which the shaft extends using aplurality of bolts at fixed bolt positions in the wall. The glandassembly includes a gland body having a first side that forms a mountingsurface for engagement with the wall of the housing and a second sidethat has a plurality of lug engaging formations, each of the lugengaging formations being characterized by a substantially straight slotformed in the second side of the gland body adjacent to the peripherythereof. The gland assembly further includes a lug member that has afirst section defining a bolt receiving aperture and a second sectiondefining a tab, the first and second sections cooperating to form arecess, the tab being dimensioned so as to be removably receivable inthe slot.

BRIEF DESCRIPTION OF THE DRAWING

The invention can be best understood by reference to the attacheddrawings in which:

FIG. 1 is an elevational, sectional view showing the mechanical sealassembly of the present invention and taken along the lines 1--1 of FIG.2;

FIG. 2 is an elevational, end view of the mechanical seal assembly shownin FIG. 1;

FIG. 3 is a partial sectional view taken along the lines 3--3 of FIG. 2;and

FIG. 4 is a partial, elevational, sectional view similar to FIG. 1 butshowing the retaining clips worn or broken away.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference first to FIG. 1, the mechanical seal assembly, showngenerally as 10, is shown attached (in a manner hereinafter described)to a machine housing 12 having a wall 14 defining a bore 16 throughwhich a shaft 18 extends, the shaft 18 being rotatable relative to thehousing 12. It will be appreciated that housing 12 can be a pump housingor a housing for any other type of machine utilizing a rotatable shaftwherein sealing is required between the housing and the shaft. Housing12 is also provided with a series of threaded bores 20 for mountingmechanical seal assembly 10 thereto, as will be described hereafter.

Seal assembly 10 comprises a gland assembly, shown generally as 22, thathas a gland body 23 that is generally annular and defines a bore 24therethrough through which shaft 18 extends. An annular gasket 26received in an annular counter bore 28 in one side wall of gland body 23serves to effect a fluid tight seal between housing 12 and gland body 23when gland body 23 is secured to housing 12.

As is conventional, the mechanical seal assembly of the presentinvention comprises a rotating assembly and a stationary assembly. Withreference first to the rotating assembly, a sleeve 30, in surroundingrelationship to shaft 18, is secured to shaft 18 for rotation therewithby means of a set screw 32 extending through a threaded bore 34 in anannular collar 36 that is disposed in surrounding relationship to sleeve30. As best seen in FIG. 1, bore 34 is in register with a bore 38 insleeve 30 whereby set screw 32 locks collar 36 to sleeve 30, bothassemblies being locked to shaft 18 for rotation therewith by means ofset screw 32. Sealing between sleeve 30 and shaft 18 is effected by anO-ring seal 40.

Received in surrounding relationship to sleeve 30 is a first, annularrotating seal element 42 defining a first sealing face 44. First sealelement 42, which can be made from a variety of materials well known tothose skilled in the art and commonly used in mechanical sealassemblies, is sealed against sleeve 30 by means of packing rings 46 andO-ring seal 48. At least one, and preferably two, drive pins 50 arepress-fitted into bores 52 in a radially outwardly projecting annularflange portion 54 of sleeve 30, bores 52 being in register with recesses56 in first seal element 42 such that as sleeve 30 rotates, pins 50,being keyed to the first seal element 42, cause rotation of seal element42 therewith. As can be seen, first seal element 42 is essentially heldbetween flange 54 and a snap or retaining ring 58 received in a groove60 in collar 30. It will thus be seen that, with respect to the rotatingseal assembly of the mechanical seal of the present invention, shaft 18,sleeve 30, collar 36, and first seal element 42 are locked togetherwhereby they all rotate relative to housing 12 and gland body 23.

With reference now to the stationary seal portion of the mechanical sealassembly 10, gland body 23 is secured to housing 12 by means of threadedstuds 62 that are received in threaded bores 20 of housing 12. Althougha fewer number can be employed, generally there are four such studs 62and four such bores 20. Removably attached to gland body 23 are one ormore lugs or brackets shown generally as 64. Each of said lugs 64 (seeFIGS. 1 and 2) comprises a first section defining a U-shaped opening 66formed by spaced apart legs 66a and 66b and a second section forming agenerally rectangular tab 68. Tab 68 projects generally perpendicular tolegs 66a and 66b.

Again, as can best be seen with reference to FIGS. 1 and 2, gland body23 is provided with a series of straight slots 70 spaced at generally90° intervals around and closely adjacent to the periphery of gland body23. Each of said slots 70 is formed in a second side wall or surface 72of gland body 23. As can be seen, slot 70 is formed on a milled-outsegment 74 of surface 72. Additionally, the peripheral edge 76 ofmilled-out segment 74 is essentially straight and parallel to slot 70,slot 70 and edge 76 cooperating to form a projecting lip 78. As will beseen hereafter, this projecting/receiving formation interlock formedbetween gland body 23 and lug 64 allows lug 64 to be easily, butremovably, positioned on gland body 23 once gland body 23 has beenpositioned around the shaft 18.

The biasing or compression spring assemblies of the present inventionare best seen with reference to FIGS. 1, 2, and 4. As shown in FIG. 2,there are four such compression spring assemblies, each of whichcomprises a spring pin 80 secured to gland body 23, spring pin 80 beingpress-fitted into a bore 82 in wall 72 of gland body 23, each of thefour pin assemblies being spaced at 90° intervals around gland body 23.In surrounding relationship to each spring pin 80 is a coil compressionspring 84. A retaining clip 86 carried by spring pin 80 serves as a stopagainst which one end of spring 84 abuts. Each of spring pins 80 extendsthrough a respective bore or slot 88 formed in an annular compressionring 90, bores 88 being spaced and positioned on compression ring 90 soas to be in register with bores 82 formed in gland body 23. A second orstationary seal element 92 is disposed between compression ring 90 andfirst seal element 42, second seal element 92 forming a second seal face94 that, as will be seen hereafter, is engageable with first seal face44 on first, rotating seal element 42. To prevent rotation of stationaryseal element 92, compression ring 90 is provided with a plurality ofrotation pins or projections 91 that are received in registering boresor recesses 91a in stationary seal 92. Like seal element 42, sealelement 92 can be made from a variety of materials commonly used inmechanical seal assemblies. Spring 84 is sized such that when spring pin80 is received through aperture 88 of compression ring 90, spring 84 iscompressed between retaining C-clip 86 and compression ring 90. This inturn urges or biases compression ring 90 against second seal element 92,forcing second seal face 94 against first seal face 44.

Spring pin 80 is provided with a second retaining C-clip 96 axiallyspaced from first retaining C-clip 86. Rotatably received on pin 80 inthe space between clips 86 and 96 is a clip 98. Clip 98, as seen in FIG.2, has a peripheral edge 100. It can be seen with particular referenceto FIG. 1 that if seal faces 44 and 94 are pressed together by virtue ofmoving flange 54 relative to gland body 23 toward collar 36, spring 84is placed in compression between compression ring 90 and retaining clip86. This preloads seal faces 44 and 94. If at this point clip 98 isrotated such that it is received in an annular, radially outwardlyfacing groove 108 formed in collar 36, this preload is retained. In theposition shown in FIG. 1, spring 84 is under compression and urgescompression ring 90 against second or stationary seal element 92.Because collar 36 is prevented from moving axially away from first sealelement 42 because of retaining clip 37 and/or screws 32, seal faces 44and 94 are thus biased into engagement with one another. Accordingly,the presence of retaining clips 98 received in the groove 108 acts tohold the preload of the stationary seal 92 against the rotating seal 42and also prevent any relative axial movement between such seals.Furthermore, the clips 98 maintain the components in coaxialrelationship to one another. Seal clips 98 are designed to release uponstart-up, i.e., on commencement of rotation of shaft 18. In other words,clips 98 will rotate out of engagement with groove 108, therebyminimizing any frictional heat buildup. Additionally, thisself-releasing ability of the clips 98 makes them potentially reusable,although, being relatively inexpensive items, should they break duringusage, they can be replaced at minimum cost.

The clips 98 are effectively, selectively removable. As noted above, theclips 98 are made of a plastic or some other frangible or wearablematerial and, because they ride in groove 108, do not have to be movedor rotated out of groove 108 once the seal assembly has been completelyinstalled. Indeed, during operation, it is highly likely and it iscontemplated that the clips 98 will wear to the point at which they willsimply break off of the spring pins 80. Such a condition is shown inFIG. 4, where the clip 98 is shown as completely missing from theassembly. Alternately, the clips 98 can be rotated out of groove 108once the seal assembly is installed. In any event, since spring pin 80is fixedly secured to gland body 23, spring 84 is held in compressionbetween retaining clip 86 and compression ring 90 whereby compressionring 90 acts to bias fixed seal element 92 against rotating seal element42.

With respect to the spring assemblies, it is to be noted that thecompression spring 84 is supported entirely on its inside diameter andis completely unsupported and visible on its outside diameter. Further,spring 84 is positioned radially outwardly from first and second sealelements 42 and 92 and thus is essentially isolated from the processfluid against which the seal assembly 10 is acting. In this regard notethat an O-ring 110 is disposed in surrounding relationship to stationaryseal 92 and forms a seal between stationary seal 92 and gland body 23.Accordingly, there is formed an annular chamber 112 in surroundingrelationship to seal faces 44 and 94. Accordingly, any process fluidleaking between shaft 18 and housing 12 is essentially trapped inchamber 112. This isolation of compression springs 84 from the processfluid ensures that the compression springs 84 will not be subjected, forexample, to any corrosive process fluids and particulates that mightleak out of chamber 112.

As best seen with reference to FIG. 3, gland body 23 is provided withthe port 114, which is in open communication with chamber 112. While inthe usual case port 114 is sealed off by a suitable threaded plug, port114 affords the opportunity to flush chamber 112, and hence the sealfaces, with a suitable fluid to effect cleaning of the seal faces orcirculate a coolant or to inject a buffer fluid to act against theprocess fluid.

A particular feature of the mechanical seal of the present invention isthe fact that not only are the compression springs 84 readily visiblesuch that clogging, or any corrosion or the like can be readilydetected, the unique positioning of compression ring 80 versus glandbody 23 allows readily visual inspection of the degree of wear on theseal faces 44, 94. In this regard, by using a suitable feeler gauge, theaxial spacing between disk 90 and gland body 23 (shown on X in FIG. 4),and hence the loading on the seal from 44, 94, can be determined.Further, this axial spacing between the compression ring 90 and thegland body 23 can be periodically checked to determine the degree ofwear of the seal faces, particularly the stationary seal face 94.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof, and various changes in the size,shape, and materials, as well as in the details of the illustrativeconstruction, may be made within the scope of the appended claimswithout departing from the spirit of the invention.

What is claimed is:
 1. A pre-loaded, cartridge-type mechanical seal foreffecting sealing between a rotatable shaft and a wall through whichsaid shaft extends and rotates relative thereto, comprising:an annularsleeve for securing to said shaft, said sleeve having a first axial endand a second axial end; a first annular seal assembly carried by saidsleeve, said first seal assembly comprising:a radially outwardlyextending flange adjacent said first axial end of said sleeve androtatable therewith; a first annular seal element disposed insurrounding relationship to said sleeve and operatively connected tosaid flange so as to be rotatable in response to rotation of said shaft,said first seal element having a first seal face; and a locking collaradjacent said second axial end of said sleeve for locking said sleeve tosaid shaft whereby said collar and said sleeve rotate in response torotation of said shaft; a second annular seal assembly, comprising:anannular housing for securing to said wall, said annular housing beingreleasably secured to said locking collar to permit said locking collarto rotate relative to said housing when said sleeve is secured to saidshaft; a second, annular seal element disposed in surroundingrelationship to said sleeve and operatively interconnected to saidhousing and having a second seal face engageable with said first sealface; and a plurality of compression spring assemblies for biasing saidsecond seal towards said first seal such that said first and second sealfaces are in sealing engagement, each of said compression springassemblies, comprising:a pin member attached to said housing, said pinmember being disposed generally parallel to said sleeve; a stop membercarried by said pin member, said stop member being disposed distal saidhousing; a compression ring having a first side operatively engageablewith said second seal element and an opposite, second side; and acompression spring disposed in surrounding relationship to said pinmember and compressed between said compression ring and said stop memberwhereby said compression spring serves to bias said second seal elementagainst said first seal element, said compression ring being unsupportedon its outside diameter for its entire length, said sleeve, said lockingcollar, and said first and second seal assemblies comprising acartridge.
 2. The mechanical seal of claim 1 wherein there are four ofsaid compression spring assemblies disposed around said sleeve.
 3. Themechanical seal of claim 1 wherein said compression ring includes anaperture through which said pin member extends.
 4. The mechanical sealof claim 1 where said compression ring is axially spaced from saidhousing.
 5. The mechanical seal of claim 1 wherein the end of said pinmember distal said stop member is received in a bore in said housing. 6.The mechanical seal of claim 1 wherein said first side of saidcompression ring is in engagement with second seal element.
 7. Themechanical seal of claim 1 wherein there is a first resilient sealbetween said first seal element and said sleeve and a second resilientseal between said second seal element and said housing to thereby definean annular chamber radially outwardly of said first and second sealfaces.
 8. The mechanical seal of claim 7 including a port in saidhousing communicating with said annular chamber.
 9. A mechanical sealfor effecting sealing between a rotatable shaft and a wall through whichsaid shaft extends and rotates relative thereto, comprising:a rotatingseal assembly, comprising:an annular sleeve for securing to said shaft;a first, annular seal element carried by said sleeve and rotatabletherewith in response to rotation of said shaft, said first seal elementhaving a first seal face; and a stationary seal assembly, comprising:anannular housing for securing to said wall; a second, annular sealelement interconnected to said housing and having a second seal faceengageable with said first seal face; biasing means for urging at leastone of said first or second seal elements toward the other of said firstor second seal elements whereby said first and second seal faces aresealingly engaged; and selectively releasable means interconnecting saidrotating seal assembly and said stationary seal assembly to restrainrelative axial movement between said rotating and stationary sealassemblies prior to securing said housing to said wall and effecting apreload of said biasing means.
 10. The mechanical seal of claim 9wherein said biasing means includes a pin member attached to saidhousing and disposed generally parallel to said sleeve, a stop membercarried by said pin member, said stop member being disposed distal saidhousing, a compression ring having a first side operatively engageablewith said second seal element and an opposite, second side, and acompression spring disposed in surrounding relationship to said pinmember and compressed between said compression ring and said stop memberwhereby said compression ring serves to bias said second seal elementagainst said first seal element.
 11. The mechanical seal of claim 10wherein said selectively releasable means comprises a clip membermounted on said pin member axially outwardly from said compressionspring, said rotating seal assembly further including a collar insurrounding relationship to said sleeve and fixed for rotationtherewith, said collar including a recess for receiving at least aportion of said clip member.
 12. The mechanical seal of claim 11 whereinsaid recess comprises an annular groove in said collar.
 13. Themechanical seal of claim 11 wherein said clip member is comprised of areadily wearable material relative to the material of said collar.